Honestly, this whole thing sickens me as a man. I see it all the time. Grocery stores, book stores, everywhere. I don't understand what drives guys to do this. I used to be single and desperate, like any guy, and would see a cute girl out somewhere and think I'd like to talk to her, but if they were working or whatever I wouldn't bother them unless I actually had a reason to talk to them. Buying an ice cream cone from a cute girl in the summer, sure, thank them with a smile and give them a nice tip and wish them a good day. That's it. That's the extent of the interaction one should expect. If you see the same girl six times that season and you introduce yourself the third time and ask how they enjoy the job and they open up to you a bit and you made a good impression and they remember you and then you figure maybe, just maybe you can talk to her outside of a contractual obligation, and maybe then you say "Hey, I know you probably get this a lot and are tired of hearing it, but I wanted to ask if you'd be interested in getting a bite to eat if you're free sometime. I know it's awkward, and its cool if you're not, and I don't mean to put you on the spot, so just think about it and next time I stop by let me know? And thanks for the sundae, and for always giving me extra nuts, the others always short change me and it kind of made me feel special when you did it, though you probably do it for everybody."

If you get a "no, I don't do it for everybody" sort of response and "sure i'd love to" then hey, good for you. Rare that it happens, but hey, I've gotten lucky before.

Sorry you have such a rough time though. Often there's nothing you can do about it just being you. A girl in a bookstore is like a girl in a comic book store I guess. And since you are on the floor and not behind a register you are more approachable. Maybe ask to do more register work so you arent on the floor as much? Or try perfecting your "dont talk to me" glare. Only, then youll get told a dozen times a day to try smiling more. Some guys just dont have any common sense or decency. They're guided by their lower brain.